Turning 49 gave me the kick in the butt I needed to finally do something about the extra weight I'd gained in my 30s and 40s. Thanks to my high-stress marketing career and the onset of menopause, I'd put on about 20 pounds. I knew my husband was going to throw me a huge 50th-birthday party, and I wanted to look phenomenal for it. I had one year to slim down—it was now or never.

Up until that point, my fitness routine included a few step aerobics and spinning classes each week, but it was getting stale and not giving me the results I wanted. So I met with Matt Pack, a trainer at my gym, to see what else I could do. He told me that to really change my body, I needed to start strength training, which would boost my metabolism and give me muscle tone so that I'd look great in any party dress. I was a bit skeptical, thinking I'd end up looking bulky, but I decided to give his plan a shot. He promised to make each workout fun, so I signed up for a month of training.

Matt kept his end of the deal, and during our first session, he had me doing really cool stuff, like whacking a tractor tire with a sledgehammer. By the end of the workout, I was exhausted but hooked. A few sessions later, he even had me climbing ropes on a tree—with help when needed. Each workout was challenging, but I felt like I was playing at recess for adults, not exercising. After that month of solo training, I'd lost body fat, and I was already starting to see a difference in how well my clothes fit. Then Matt suggested that I join one of his small-group classes. I took him up on it, and I'm so glad I did, because that's where I ended up meeting the women whom I now call my best friends.

Sweat soul mates
I used to socialize at the office, but I launched my own marketing company in my 40s and now work from home. I feel isolated most of the day, so working out with a group of eight women offered the perfect way to find new pals. There's something intimate about sweating alongside someone that really forges a bond. We trained together three times a week, and Matt nicknamed us his Strong Women group—which is exactly how we felt.

Around that time, I also changed my diet and began following the Paleo meal plan. This basically involves eating only what was available to cavemen, including lots of fruits, vegetables, nuts, seafood, and meat. I noticed that when I cut out all the junk, I had more energy throughout the day. By the time my 50th birthday rolled around, I was two sizes smaller and 9 pounds lighter.

A few months later, it became too expensive for most of the Strong Women and me to continue our private training, so we sought out other fun ways to keep exercising together. To get our sweat fix, we found fun deals on Groupon and Living-Social for classes at local fitness studios. One of the best deals was for a month of CrossFit workouts, which is a strength and conditioning program that mixes sprinting, rowing, and other forms of high-intensity cardio with functional strength exercises, such as push-ups and dead lifts. We all signed up and soon were doing pull-ups and swinging kettlebells right alongside a lot of younger, superfit people—and having a blast. (See how you can get a flat belly with kettlebell swings.)

Normally I might feel insecure, but when I turned 50, I had the freeing realization that while I might not get a wolf whistle when walking down the street, I could do whatever I wanted, because no one was paying attention. So I wasn't self-conscious sweating next to a 20-something guy with great pecs at CrossFit, because I knew he wasn't looking at me. But that didn't mean I couldn't enjoy looking at him!

Adventure is knocking
The Strong Women gals and I even take our workouts on the road, turning far-flung races into fun-filled, girlfriend-getaway weekends. We've completed a stair-climbing race and participated in a mud and obstacle course together called the Warrior Dash that had me, at just shy of 53, crawling under barbed wire and jumping over fire pits. I discovered that doing something challenging isn't intimidating; it's liberating and makes crossing the finish line all the more empowering and enjoyable. After washing off the mud, we went to a rodeo to celebrate our accomplishment.

I truly love being over 50. I exercise so that I can be active for life—and so I can keep drinking wine and eating cheese without worrying about what my bathroom scale says! While I've slimmed down and lost 18 pounds over the past 5 years, meeting my new friends is by far the best thing that staying fit has done for me. (Get inspired by other women who love their age, here.)

3 fun fitness events to do with your girlfriends

Discover your strength and prove that women run the world by joining one of Iron Girl's events, ranging from 5-K races to sprint triathlons. (irongirl.com)

Check out the Illuminite Run, which turns a 5-K into a nighttime neon bash complete with a lighted course and glow-stick afterparty. (illuminiterun.com)

Dive into a mud pit at Dirty Girl, an untimed women-only 5-K mud and obstacle race that will have you feeling like an alpha female warrior. (godirtygirl.com)